Grease composition and hub unit

A hub unit in which a grease composition is enclosed, the hub unit comprising:

• a hub wheel;
• an outer ring;
• an inner ring member;
• a plurality of balls;
• and
• two seal members,
• wherein the grease composition is enclosed in an annular space formed by the outer ring, the hub wheel, and the two seal members,
• wherein the grease composition comprises a base oil, a thickener, and an additive, wherein:
• the base oil contains a synthetic oil;
• the thickener contains a compound having a urea group;
• and
• the additive contains a phosphoric compound, a calcium-based compound, and a hydrocarbon-based wax;
• wherein
• the synthetic oil is a mixed oil including a poly alpha olefin oil and an ester oil;
• the ester oil is a pentaerythritol ester;
• a ratio of the ester oil to the base oil is 5 to 15 mass %, and a ratio of the poly alpha olefin oil to the base oil is 85 to 95 mass %;
• the phosphoric compound is an amine phosphate;
• a content of the amine phosphate in the grease composition is 0.05 to 5 mass %;
• the calcium-based compound is an overbased calcium sulfonate;
• the overbased calcium sulfonate has a base number of 50 to 500 mgKOH/g;
• a content of the overbased calcium sulfonate in the grease composition is 0.05 to 5 mass %;
• the hydrocarbon-based wax is-consists of a polyethylene wax;
• and
• a content of the polyethylene wax in the grease composition is 0.05 to 5 mass %.